You have to secure the box to something. It can be a crossmember as you mention, or if it's only a few inches, you can just add a short piece of stud between the box and the real stud.

A framer won't generally care about the electrical layout. If there is some compelling reason that an box or any other issue compels a stud to not be located in a specific place, you need to make sure the framer's instructions accurately reflect that.

I have a question on using old work boxes in new construction before closing. When my home was built in 95 we had additional outlets installed once we actually saw where we may need them. The builder used old work boxes which attach to the sheetrock. Was that to code? I'm also assuming the total number on the circuit was to code after we added the outlets.

It could be to code. Nothing prohibits an old work box in new construction. However, if the walls are open when the wiring is run, you're expected to meet the cable attachment rules. If he fished the wire in after the wall was closed up then that's a different story. The NEC doesn't really put any practical limit on 120V 15/20A receptacles on a circuit in dwellings. The only issue to watch that you've not put outlets for other rooms on the ones reserved for special use (kitchen receptacles, bathrooms, laundry areas).

Thanks, I always thought there was a limit on outlets.

Thanks, I always thought there was a limit on outlets.
Not for multiple receptacles on 120V 15/20A branches in dwelling uses (in the US).

I wouldn't put an old work box in the middle of an open span of drywall, if the outlet is going to be used frequently. Plugging and unplugging will eventually cause the drywall to crack.

Boxes can be fastened to fireblock/horizontal members between studs, to 1x4 or 2x4 sisters attached along a stud, to metal support frames or struts (like fan boxes and recessed cans are), or to any solid framing member. They should always be well fastened, screws are better than nails (easier to do right).